Drawing instrument

ABSTRACT

A drawing instrument in which a Y-rail is connected at right angles to an X-rail firmly secured to a drawing board along an Xcoordinate axis and permitted to move in sliding motion relative to the X-rail, and in which ruler means with graduated scales is connected to a head mounted on a Y-carsol slidably mounted on the Y-rail. The head is provided with resilient means for urging the ruler means connected to the head to move upwardly away from the surface of the drawing board for facilitating operation of the ruler means.

United States Patent 1191 Yada et al. July 9, 1974 I DRAWING INSTRUMEN'I 3,363,319 H1968 (IIUCI 33/76 R 75] Inventors: Tatsuo Yuda; Yoshibumi FOREIGN PATEN'I'S OR APPLICATIONS fi g fl h Waianabe, 116,526 6/1946 Sweden 33/79 R a o 0 yo, apan [73] Assignee: Mu'to Industrial Company Ltd., Prima'y Examiner-Harry Hamian Tokyo, Japan Attorney, Agent, or FzrmWenderoth, Lind & Ponack [22] Filed: July 21, 1971 [57] ABSTRACT pp No: 164,766 A drawing instrument in which a Y-rail is connected at right angles to an X-rail firmly secured to a drawing 52 us. c1 33/76 R board along an x-coordinatfi axis and Permitted to 51 Int. Cl B431 13/02 move in Sliding motion relative to the x-rail, and in [58] Field of Search 33/76 79 which ruler means with graduated Scales is Connected to a head mounted on a Y-carsol slidably mounted on [56] References Cited the Y-rai]. The head is provided with resilient means for urging the ruler means connected to the head to UNITED STATES PATENTS move upwardly away from the surface of the drawing Q board for facilitating operation of the ruler means. occa I... 3,343,267 9/1967 Wolf 33/79 R 3 Claims, 8 Drawing Figures 102 B8 26 m m 1 2 131 14g 13 1211 123 m3 r 59' 211 J 111 5 114 I fl )JIIII 13513 1 11s if, 1!. l m 1311 1 111 152 7 "H14 I53 50 1/ 11' 7/ 11 MB 1 1 7 1 1 129 11B 121 117 1111 A mzmmm 3322.474

' sum 1 or a E D 172 154 I62 INVENTOR s TATSUO YADA, YOSHIBUMI KOMABAYASHI and YOSHINORI WATANABE ATTORNEY s E H s INVENTOR S TATSUQ YADA,

YOSHIBUMI KOMABAYASHI and YOSHINORI WATANABE ATTORNEYS INVENTORS TATSUO YADA,

YOSHIBUMI KOMBAYASHI and YOSHINORI WATANABE ATTORNEYS 1 BACKGROUND OF THE INVENTION This invention relates to a drawing instrument comprising, as its main elements, a head capable of moving along an X-rail and a Y-rail and parallel thereto and ruler means with graduated scales connected to the head which ruler means can be angularly rotated along the surface of a drawing board through any degree as desired by turning a handle connected to the head.

In conventional drawing instruments of the type described, the ruler and head are maintained at their undersides in contact with the upper surface of the drawing board when the ruler is moved from one position to another on the drawing board. The ruler is thus kept in frictional engagement with the paper on the drawing board whenit moves thereon. Because of this frictional engagement, the surface of the paper on which lines or other symbols are drawn may get soiled, and the paper may be torn in worst cases if the moving ruler impinges on an end portion of the paper.

Because of the frictional dragging of the ruler and head on the surface of the paper on the drawing board, the draftsman finds it hard to operate the ruler because the ruler is heaver to him than it actually is, thereby hindering realization of advantages from use of this type-of drawing instruments.

SUMMARY OF THE INVENTION A main object of this invention is to provide a drawing instrument which is provided with means for resiliently urging the ruler means or the ruler means and the head to move upwardly away from the surface of the drawing board. By causing the ruler means or the ruler means and the head to move upwardly away from the surface of the drawing board or resiliently urging the same to move upwardly away therefrom, it is possible to remove or at least minimize frictional dragging of the underside of the ruler means on the surface of paper on the drawing board, so that the ruler means can be moved easily and smoothly on the surface of the drawing board with only a small force.

Another object of the invention is to provide a drawing instrument which is provided with means for bringing the ruler means to a position in which it is disposed parallel to and in face-to-face relation with the surface of the drawing board when the ruler means or the ruler means and the head are moved upwardly away from the surface of the drawing board. To this end, the head is mounted on the Y-carsol such that the head can be movable in a direction in which the head moves away from the surface of the drawing board and, at the same time, the resilient means mounted on the Y-carsol is caused to act on the head, so that the ruler connected to the head can be moved upwardly away from the surface of the drawing board a predetermined distance by the biasing force of the resilient means. By virtue of this arrangement, if the head is moved toward the surface of the drawing board against the biasing force of the resilient means, the ruler means can readily be moved toward the surface of the drawing board into a position in which it is disposed parallel to and in face-to-face reboard by the biasing force of the resilient means. Ac-

cordingly, when it is desired to move the ruler means in the direction of the X-ordinate axis or Y-ordina-te: axis on the drawing board, the ruler. means can be moved easily and smoothly in any direction as desired by exerting on the head a force directed in the direction.

of movement of the ruler means which is parallelv to the surface of the drawing board without requiring to exert on the head an additional force for lifting it.

Another object of the invention is to provide, in a drawing instrument, resilient means for causing the ruler means to move upwardly away from the surface of the drawing board the biasing force of which can be adjusted as desired. By effecting adjustments of the biasing force of the resilient means, it is possible to regulate as desired the spacing between the underside of the ruler means and the surface of the drawing board, and it is possible to adjust the biasing force such that the underside of the head is brought into light engagement with the surface of the drawing board. Besides, it is possible to regulate the spacing between the underside of the ruler means and the surface of the drawing board such that it is kept constant at all times irrespective of the angleof inclination of the drawing board. If the drawing board is brought from a position in which its surface is parallel to the horizontal to a position in which its surface is inclined with respect to the horizontal, the load appled to the ruler means will show adecrease in its component which acts perpendicularly downwardly on the drawing board which decrease is proportional to the angle of inclination. At this time, if the biasing force of the resilient means acting on the ruler means remains constant, the distance the ruler means is moved upwardly away from the surface of the drawing board will be greater when the drawing board is inclined than when it is horizontal. In order to pre vent this condition, it is necessary to reduce the biasing force of the resilient means in proportion to an increase in the angle of inclination of the drawing board. When the drawing board is moved from a position in which its surface is inclined with respect to the horizontal to a position in which its surface is parallel to the horizontal, a phenomenon opposite to that described above will occur.

Additional objects as well as features and advantages of this invention will become evident from the description set forth hereinafter when considered in conjunction with the accompanying drawings.

According to this invention, there is provided a drawing instrument in which ruler means with graduated scales is movably connected to a head mounted on a Y-carsol slidably mounted on a Y-rail so that the ruler means can be moved into contact with and awayfrom the surface of the drawing board, and in which resilient means is provided in the head and caused to act on the ruler means so that the ruler means can be moved upwardly away from the surface of the drawing board by the biasing force of the spring.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of the drawing instrument in its entirety according to this invention, with portions of the X-rail and Y-rail being cut out;

FIG. 2 is a vertical sectional side view of the drawing instrument of FIG. 1, with a portion of the Y-rail not being shown in section;

FIG. 3 is a plan view showing the manner in which the X-carsol is connected to the Y-rail and showing brake means;

FIG. 4 is a sectional view taken along the line A-A of FIG. 1;

FIG. 5 is a sectional view taken along the line B-B of FIG. 2;

FIG. 6 is a sectional view taken along the line CC of FIG. 1 and showing ruler fine adjustment means;

FIG. 7 is a sectional view taken along the line DD of FIG. 1 and showing base plate locking means; and

FIG. 8 is a sectional view taken along the line EE of FIG. 1 and showing protractor locking means.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION A preferred embodiment of this invention will now be described with reference to the accompanying drawmgs.

There isprovided a drawing board 11 which is constructed such that its surface can be moved from a position in which it is disposed parallel to the horizontal to a position in which it is tilted about 90 with respect to the horizontal and can be positioned at any degree as desired within the aforementioned angle of inclination. An X-rai] 12 is firmly secured to one marginal portion of the surface of the drawing board 11 in a manner shown in FIG. 2.

The X-rail 12 formed in its side wall a mounting portion 13 which is ]-shaped in cross-section and disposed lengthwise of the rail, and a mounting opening 14 is formed lengthwise of the rail in a vertical planar bar member 13a of the mounting portion. 15 is a lock member slidably fitted in the mounting opening 14 and having attached to one end thereof a flange 16 which is disposed within the hollow portion of the mounting portion 13 and in face-to-face relationship with the inner wall surface of the planar bar member 13a.

17 is an L-shaped supporter removably secured to an end portion of the drawing board 11 and having secured at its upper end portion a member 18 which is positioned against the upper surface of the drawing board 11. Threadably connected to a horizontal portion 17a formed in the lower portion of the supporter 17 is a clamp screw 19 which presses at one end portion thereof against the underside of the drawing board 11 through a washer 20. The supporter 17 includes a vertical portion 17b which is positioned against a side surface of the drawing board 11. A hole 21 having an internally threaded portion 210 is formed substantially in the central portion of the vertical portion 17b of the supporter 17 and extends as far as its lower end. The hole 21 opens substantially in the intermediate portion of a horizontal hole 22 formed in the vertical portion 17b of the supporter.

The lock member 15 is slidably fitted in the horizontal hole 22 and has formed on its inner peripheral surface a groove 23 which is formed with a tapering surface 150. 24 is an externally threaded rod threadably fitted in the internally threaded portion 21a of the hole 21. The externally threaded road 24 has a tapering end portion which is adapted to be positioned against the tapering surface 15a of the lock member 15 slidably fitted in the horizontal hole 22.

If the externally threaded rod 24 of the aforementioned construction is turned while the lock member 15 is inserted in the horizontal hole 22 of the supporter 17 to bring one end portion of the rod 24 into pressing engagemcnt with the tapering surface 15a of the groove 23 in the lock member 15, the lock member 15 will be pushed and moved upwardly and leftwardly in FIG. 2 by the one end portion of the rod 24 and displaced leftwardly within the horizontal hole 22, so that the flange 16 is brought into pressing engagement with the planar bar member 13a and the X-rail 12 is secured to the supporter 17. If the threaded rod 24 is turned in an opposite direction so as to move the one end portion thereof away from the tapering surface 15a of the groove 23, the flange 16 will be released from pressing engagement with the X-rail 12, thereby permitting the X-rail 12 to move lengthwise thereof. Also, if the threaded rod 24 is turned to withdraw the one end portion thereof from the horizontal hole 22, it will be possible to withdraw the lock member 15 from the horizontal hole and to remove the X-rail 12 from the supporter 17.

25 is an X-carsol slidably mounted on the X-rail 12. A Y-rail 26 is connected at one end thereof to the X- carsol 25. The manner in which the Y-rail 26 is connected to the X-carsol 25 is shown in detail in FIGS. 1, 2 and 3. 27 and 28 are mounting plates arranged in channels 29 and 30 respectively which are formed on opposite sides of the Y-rail 26. Support plates 31 and 32 are secured at their upper portions to the mounting plates 27 and 28 by screws 33 and 34 respectively. By being clamped by the screws 33 and 34, the mounting plates 27 and 28 are brought into pressing engagement with wall surfaces of the Y-rail 26 in which the channels 29 and 30 are formed.

The support plates 31 and 32 have lower portions which are disposed on opposite sides of a hinge 25a of the X-carsol 25 in face-to-face relationship with each other. Secured to the hinge 25a are bearings 35 and 36 which are formed with tapering holes 35a and 36a respectively. Disposed in pressing engagement with the tapering holes 35a and 36a of the bearings 35 and 36 are tapering front ends of clamp screws 39 and 40 which are adapted to be threadably engaged in internally threaded holes 37 and 38 formed in the lower portions of the support plates 31 and 32 respectively. When the tapering front ends of the clamp screws 39 and 40 are brought into pressing engagement with the tapering hoTes 3521 and itia o f thebai'ings 35a nd 36 respectively and the Y-rail 26 is connected at one end thereof to the hinge 25a of the X-carsol 25, the Y-rail 26 is disposed at right angles to the X-rail 12.

The Y-rail 26 can be moved pivotally in a vertical direction with respect to the surface of the drawing board 11 about the tapering holes 350 and 36a of the bearings 35 and 36 respectively which are secured to the X- carsol 25. Rollers 41, 42, 43 and 44 which rotate in a horizontal direction with respect to the X-carsol 25 and rollers 45, 46, 47 and 48 which rotate in a vertical direction with respect to the X-carsol 35 are rotatably supported by the X-carsol 25. The rollers 42 and 44 are positioned against one side surface of a rail 49 attached to the underside of the X-rail 12 and are disposed lengthwise thereof, and the rollers 41 and 43 are positioned against the other side surface of the rail 49. The rollers 45 and 47 are disposed on a rail formed in one side portion of the X-rail 12 and which is substantially parallel to the surface of the drawing board 11, and the rollers 46 and 48 are disposed on a rail 12b formed in the other side portion of the X-rail 12 and Y which is substantially parallel to the surface of the drawing board 11.

The rollers 45, 46, 47 and 48 are subjected to a vertically and downwardly directed load applied to the X- carsol when the latter moves and rollingly move along the rails 12a and 12b. At the same time, the rollers 41, 42, 43 and 44 rollingly move along the rail 49 while their direction of movement is guided by the rail 49 so that the rollers 41, 42, 43 and 44 may move in a straight line, thereby preventing rolling of the X-carsol 25 from side to side.

Brake means for locking the X-carsol 25 in any position as desired on the X-rail 12 will now be described. A guide groove 50 (see. FIG. 5) is formed in the Y-rail 26 and is disposed lengthwise thereof, and a movable rod 51 is slidably received in the guide groove 50. The movable rod 51 is mounted on a slider 52 by screws 53 and 54. The slider 52 is slidably mounted on the Y-rail 26 and has inwardly extending projections 55 and 56 which are slidably reeived in guide channels 57 and 58 respectively which are formed in the Y-rail 26 lengthwise thereof.

Attached to the front end of the moving member 51 is a rack gear 59 with which is maintained in meshing engagement a segmental gear 60 rotatably supported by the support plate 31 through a shaft. 61 is a cam rotatably supported on the support plate 31 on a shaft. The cam 61 includes an arm 62 which has formed at its front end an engaging groove 63 in which is slidably received a pin 64 projecting from the segmental gear 60 in an eccentric position. The cam 61 also includes a projection 61a which is adapted to press against a pressure receiving portion 65b bent up a projection 65a of a brake 65.

The brake 65 is juxtaposed at one end portion 65c thereof to one side surface of a web portion 66 formed integrally with the rail 49 of the X-rail 12, and rotatably connected at the other end thereof to one endportion of a bent brake 68 by a screw 67. The bent brake 68 is rotatably mounted substantially at its intermediate portion on the X-carsol 25 by a screw 69. The bent brake 68 is juxtaposed at the other end portion thereof to the other side surface of the web portion 66 of the X-rail 12. Friction members 70 and 71 are attached to the other end portion of the bent brake 68 and one end portion 650 of the brake 65'respectively.

72 is a spring attached to the X-carsol 25 which urges I by its biasing force one end portion of the brake 65 and the other end portion of the bent brake 68 to move outwardly. 73 is a stop for precluding the upward movement of the projection 65a of the brake 65 away from the X-carsol 25. The stop 73 is secured at one end thereof to the X-carsol 25.

If the slider 52 of the aforementioned construction is moved in sliding motion in the direction of the arrow H along the guide groove 50 of the Y-rail 26 so as to move the movable rod 51 in the direction of the arrow H, the pin 64 will pivotally move by virtue of the meshing engagement of the segmental gear 60 with the rack gear 59 so that the arm 62 of the cam 61 will move pivotally in conjunction with the pivotal movement of the pin 64, with the result that the cam 61 will rotate a predetermined amount in a clockwise direction in FIG. 2 and the projection 61 will be displaced. This causes the projection 61a of the cam 61 to push and move the pressure receiving portion 65b of the brake 65.

If the pressure receiving portion 61a is moved, one end portion 650 of the brake 65 will be brought into pressing engagement with one side surface of the web portion 66 of the X-rail 12 through the friction member 70 and against the biasing force of the spring 72. At the same time, the pressing force exerted on the brake 65 will be transmitted to the bent brake 68 which is rotated in a counterclockwise direction in FIG. 3 about the screw 69, with a result that the bent brake 68 will be brought at the other end portion thereof into pressing engagement with the other side surface of the web portion 66 of the X-rail 12 through the friction member 71 and against the biasing force of the spring 72. In this condition, the X-carsol 25 is locked to the X-rail 12. The X-carsol 25 is unlocked if the slider-52 is moved a predetermined amount along the Y-rail 26 in a direction opposite to the direction of the arrow H.

74 is a Y-carsol slidably mounted on the Y-rail 26 and shown in detail in FIGS. 1 and 4.

75, 76 and 77 are rollers disposed on horizontal rail members 78 and 79 of the Y-rail 26 and rotatably supported on shafts by mounting portions 80, 81 and 82 respectively. 83, 84 and 85 are rollers rotatably'held against vertical rail members 87 and 87a of the Y-rail 26 respectively and rotatably supported by the Y-carsol 74.

The rollers 75, 76 and 77 are subjected to a load which is applied to the Y-carsol 74, and the rollers 83, 84, 85 and 86 control the direction of movement of the Y-carsol 74 along the Y-rail 26 to cause the same to move in a straight line.

A weight 89 is slidably mounted in a weight receiving space 88 of the Y-rail 26 and connected to the Y-carsol 74 by a rope 90 which is guided by rope pulleys 91 and 92 rotatably connected to opposite end portions of the Y-rail 26. The weight 89 and Y-carsol 174 are connected to each other by the rope 90 such that, when the drawing board 11 is tilted, forces of gravity which cause them to move downwardly cancel each other. By connecting the weight 89 to the Y-carsol 74 in this way, a sudden downward movement of the Y-carsol 74 along the surface of the drawing board 11 which might otherwise be caused to occur by a force acting on the Y- carsol 74 when the drawing board 11 is moved from a horizontal position to a tilted position can be precluded. The Y-carsol 74 is caused to stop in any position as desired on the Y-rail 26 irrespective of the tilting of the drawing board by a pull-up force proportional to the angle of tilting of the drawing board 11 which is produced by the force of gravity acting on the weight 89. i

93 is a tail roller rotatably attached to the other end of the Y-rail 26 and adapted to be rotatably positioned against the surface of the drawing board 11. When the tail roller 93 is positioned against the surface of the drawing board 11, the Y-rail 26 is disposed parallel to the surface of the drawing board 11. Brake means for locking the Y-carsol in any positio as desired on the Y-rail 26 will now be described. 94 is a lever pivotally supported by the Y-carsol 74 on a shaft. The lever 94 has at one end portion a pusher 940 which is positioned against a side portion of a bent brake 95. The bent brake 95 has formed at one end portion thereof a bent portion 95a which has attached thereto a friction member 96 which is positioned against an outer side surface of the vertical rail 87a formed in the Y-rail 26. The bent brake 97 is rotatably connected at one end portion thereof to the other end portion of bent brake by a screw 98. The bent brake 97 is rotatably mounted substantially at its intermediate portion on the Y-carsol 74 on a screw 99. The bent brake 97 has formed at the other end thereof a bent portion 97a which is positioned against an outer side surface of the vertical rail member 87 of the Y-rail 26 and which has attached thereto a friction member 100. 101 is a spring connected to the Y-carsol 74 by a screw which urges by its biasing force one end portion of the bent brake 95 and the other end portion of the bent brake 97 away from each other.

If the lever 94 of the aforementioned construction is moved pivotally in the direction of the arrow 1, the pusher 94a of the lever 94 will be displaced and push and move the bent brake 95 leftwardly in FIG. 1, so that the bent portion 95a of the brake 95 is brought into pressing engagement with the vertical rail member 870 of the Y-rail 26 through the friction member 96. At the same time, the pressing force exerted by the pusher 94a is transmitted to the bent brake 97 and causes the same to pivotally move in a clockwise direction about the screw 99, so that the bent portion 97a of the brake 97 is brought into pressing engagement with the vertical rail member 87 of the Y-rail 26 through the friction member 100 and the Y-carsol 74 is locked in any position as desired on the Y-rail 26.

1f the lever 94 is returned to its original position, the Y-carsol 74 will be unlocked and rendered free to move along the Y-rail 26.

102 is a head which is mounted on the Y-carsol through a head connecting mechanism 103 which is shown in detail in FIGS. 1 and 4. The head connecting mechanism 103 will now be described.

Mounting blocks 104 and 105 spaced apart a predetermined distance from each other are provided on the Y-carsol 74 in face-to-face relationship with each other. The mounting blocks 104 and 105 are formed with internally threaded bores 106 and 107 respectively which are disposed on a straight line.

The head 102 includes a member 108 attached thereto and having formed at one end portion thereof mounting blocks 109 and 110 which have internally threaded bores (not shown) respectively which are disposed on a straight line.

111 is a connector which is held on opposite side surfaces thereof for pivotal motion by clamp screws 112 and 113 and 114 and 115 threadably engaged .in the mounting blocks 104 and 105 and 109 and 110 respectively. The clamp screws 112 and 113 are disposed on a straight line, and the clamp screws 114 and 115 are disposed on a straight line. These clamp screws taper at their front ends and their tapering front ends are rotatably pressed into tapering bores of four shaft supporters 116 secured to opposite side surfaces of the connector 111.

117 is a connecting link which has a relief slot 118 at one end portion thereof and which is pivotally mounted on a projection 120 of the member 108 on a screw 119. A screw 121 secured to the Y-carsol 74 has a stem which is slidably received in the relief slot 119 formed in the connecting ring 117. The screw 121 is normally disposed at the right end of the relief slot 118 in FIG. 4. Assuming that the line connecting the clamp screws 112 and 113 at their center is A and the line connecting the clamp screws 114 and 115 at their center is B, then the lines A and B are parallel to each other. Assuming that a line connecting the two lines A and B togther and disposed normal thereto is C, then the line C has a length which is equal to the length of the line D connecting the center of the screw -119 with the center of the screw 121 which screws support the connecting link 117 at opposite ends thereof. The lines C and D are parallel to each other.

Accordingly, the head connecting mechanism 103 is constructed in the from of a pantagraph mounting mechanism. 122 is a square guide opening formed on the underside of the connector member 111 for slidably receiving a slide block 123 therein. 1 24 is a threaded rod threadably connected to the block 123 and inserted in a bore 125 formed in the connector member 111. The threaded rod 124 is rotatably positioned by means of a head 126 and a flange 127. The head 126 has a knob 128 attached thereto.

129 is a plate spring which is secured at one end portion thereof to the Y-carsol 74 by screws and is maintained at the other end portion thereof in contact with the underside of the slide block 123, so that the member 108 is urged to move upwardly by the biasing force of the plate spring 129 through the slide block 123.

130 is a handle of the head 102 which is rotatably secured to a rotary tube 133 by nuts 131 and 132. 134 is an outer tube fitted within a tubular portion 108a of the member 108 and having a flange 134a projecting from the outer peripheral surface of the lower portion thereof and threadably engaged by a nut 135.

By turning the nut 135 in a direction in which it is tightened against the screw, the nut 135 and flange 134a can be brought into pressing engagement with the upper and lower surfaces of the tubular portion 1080 respectively, so that the outer tube 134 is firmly secured to the member 108. 136 is a nut for preventing loosening of the nut 135 which threadably engages a threaded portion formed on the upper portion of the outer tube 134 to press against the nut 135.

137 is a protractor slidably fitted over the outer peripheral surface of the flange 1340 of the outer tube 134. The protractor 137 has formed in its upper surface an annular groove 138 of convex-shaped cross-section and has an index ring 139 secured to its underside. The index ring 139 has formed on its outer peripheral surface engaging recesses 140 which are spaced apart from one another a distance corresponding to an angle of 15. 141 is a scale indicator attached to the upper surface of the protractor 137 and calibrated in degrees. 142 is an operation lever connected at one end portion thereof to the upper end of a conical rod 142 disposed in therotary tube 133 and having, in a suitable position, an opening 144 for receiving therein a stop 143 of the handle 130 when the lever 142 is pushed, lengthwise thereof.

145 is a base plate attached to the flange 1330 of the rotary tube 133 and pivotally supporting one end portion of a lock pawl member 146 on a shaft. The member 146 has formed at the outer end thereof a pawl which is disposed against the engaging recesses 140 of the index ring 139 and shaped such that it is adapted to be received in one of the engaging recesses 140.

A shaft 147 is mounted on the lock pawl member 146 substantially midway between opposite ends thereof and is rotatably connected to one end of a connecting rod 148 which is connected at the other end portion thereof to the lower end portion of the conical rod 142. The connecting rod 148 is urged by the biasing force of a spring 149 to move upwardly and leftwardly in FIG. 4.

150 is a lower cover firmly secured to the base plate 145 by rings 151 and 152. The lower cover 150 has formed on the underside thereof a plurality of convex curve portions 150a so that the underside of the lower cover 150 will be maintained in point contact with the surface of the drawing board 11 through the convex curve portions 151. v

152 is an upper cover made of a transparent material and attached to the lower cover 150. The upper cover 152 has superposed on its upper surface an index 152a which indexes with the scales of the scale indicator 141. Angular displacements of the base plate 145 can be indicated quantitatively by changes in the relative positions of the index 152a and the protractor 137 when the base plate 145 is angularly rotated.

153 is a ruler mounting plate rotatably supported by the base plate on a shaft. A fine adjustment 154 is mounted on the ruler mounting plate 153 in a position which is spaced apart a predetermined distance from the position in which the cover 152 is supported by the base plate 145. The fine adjustment 154 is shown in detail in FIG. 6. Openings 155 and 156 are concentrically formed in the base plate 145 and ruler mounting plate 153 respectively in portions thereof which are connected together, the opening 156 slidably receiving the threaded rod 157 therein and the opening 155 loosely receiving the threaded rod 157.

As seen in FIG. 6, 158 is an eccentric plate rotatably fitted in an eccentric position over the threaded rod 157 and having an outer peripheral surface which is rotatably fitted in the opening 155. 159 is a presser integral with the eccentric plate 158 and rotatably fitted over the threaded rod 158. 160 is an internally threaded tube which threadably receives therein the threaded rod 158. The internally threaded tube 160 has an upper portion which is secured to a lever 162 by a screw 161. The tube 160 is juxtaposed at its lower end surface with the upper surface of the presser 159.

163 is a flange attached to the lower end of the threaded rod 157 and juxtaposed to the underside of the base plate 145. 164 is a vertical ruler member and 165 is a horizontal ruler member. The two members 164 and 165 are removably connected to the ruler mounting plate 153 by screws 166 and 167. When the convex curve portions 150a of the lower cover 150 are in contact with the surface of the drawing board 11, the ruler members 164 and 165 are maintained in a horizontal position and in contact, at their underside, with the surface of the drawing board 11.

FIG. 7 shows base plate lock means 168. Rotatably fitted in an opening 170 formed in the base plate 145 is a threaded rod 169 having attached to its lower end portion a flange 171 juxtaposed to the underside of the base plate 145. An internally threaded tube 173 having an angle lever 172 attached thereto is threadably fitted over the upper portion of the threaded rod 169. 174 is a brake block slidably fitted over the threaded rod 169. The brake block 174 has one end portion 174a slidably disposed between the underside of the portractor 137 and the upper surface of the index ring 139. A project ing lower end surface 17412 of the internally threaded tube 173 is positioned against the upper surface of the brake block 174.

175 is protractor lock means which is shown in detail in FIG. 8 in which an internally threaded member 176 is slidably fitted in an opening 177 formed in the manner 108 so that a flange 176a attached to the outer peripheral surface of the member 176 is positioned against the upper surface of the member 108. A; threaded rod 178 is threadably received in theintera nally threaded member 176 to which a base line lever. 179 is secured by a screw 180. Formed at one end; of

the threaded rod 178 integrally therewith is a flange 181 which is slidably received in the annular groove 138 of the protractor 137. v

If the handle of the aforementioned construction is turned, the rotation of the handle 130 will be transmitted to the rotary tube 133, base plate 145, ruler mounting plate, ruler members 164 and, 165, lock pawl; member 146, index ring 139 formed with the engaging recesses adapted to receive the pawl of the member 146, and protractor, so that it is possible to move the ruler members 164 and 165 into any angular position as desired. In this condition, the base plate is set an angle of 0 with respect to the protractor 137.

After the handle 130 is rendered free to rotate, either one of the ruler members 164 and is brought into index with the base line of a drawing sheet on the drawing board 11 and the base line lever 179' is pivotally moved so as to rotate the internally threaded member 176. in a direction in which the threaded rod 178 moves upwardly. This will bring the flange 181 of the threaded rod 178 into pressing engagement with the annular groove 138 and the flange 176a of the internally threaded member 176 into pressing engagement with the upper surface of the member 108. By being held between the two flanges 176a and 181, the protractor 1.37 is locked with respect to the member 108.

When it is desired to tilt the ruler members 164 and 165 by about 15 with respect to the base line, the operation lever 142 is pushed lengthwise thereof so as to. pivotally move the conical rod 142 in an a counterclockwise direction in FIG. 4 within the rotary tube 133 about a major diameter portion 142a thereof. Rotary displacement of the conical rod 142 will move theconnecting rod 148 rightwardly along the underside of the base plate 145. The shaft 147 coupled to the connecting rod will also move rightwardly, causing the lock pawl member 146 to move pivotally at one end portion thereof so as to release its pawl from engagement with one of the engaging recesses 140 of the index ring 139.

When the lock pawl member 146 is released from engagement with the index ring 139, the base plate 145. is rendered free relative to the protractor 137. In this condition, if the handle 130 is turned to angularly move the base plate 145 and if a pressing force exerted on the operation lever 142 is removed, the connecting rod 148 will be urged by the biasing force of the spring 149 to. return to its original position and the pawl of the lock pawl member 146 will be brought by the biasing force of the spring 149 into resilient engagement with the outer peripheral surface of the index ring 139 till the pawl is received in engagement with another or adjacent engaging recess 140, so that the base plate 145 is.

locked with respect to the index ring 139 through the lock pawl member 146.

As aforementioned, the engaging recesses 140 are spaced apart from one another a distance correspond:

ing to an angle of 15, so that the ruler members 164 mentioned operation. By fitting the stop 143 in the opening 144 formed in the lever 142, it is possible to lock the lever 142 in a position to which it has been pushed and moved.

By pivotally moving the angle lever 172, it is possible to lock the base plate 145 with respect to the protractor 137 at any angle as desired while the lock pawl member 146 is being released from engagement in the engaging recesses 140 of the index ring 139. Pivotal movement of the angle lever 172 will result in the brake block 174 being pressed by the underside of the internally threaded tube 173 and one end portion of the block 174 being brought into pressing engagement with the upper surface of the index ring 139, so that the base plate will be locked with respect to the protractor 137.

When it is desired to effect fine adjustments of the angle between the ruler mounting plate 153 and the base plate 145 in a direction parallel to the surface of the drawing board by pivotally moving the ruler mounting plate 153 about its pivot while the base plate 145 remains fixed, the presser 159 is moved to rotate the eccentric plate 158 within the opening 155. Since the center of rotation of the eccentric plate 158 is immovably held by the threaded rod 157, rotation of the eccentric plate 158 will result in the ruler mounting plate 153 being slightly displaced an amount corresponding to the amount of eccentricity of the eccentric plate 158. If the lever 162 is turned in a direction in which the tube 160 is clamped onto the threaded rod 157, the connecting portions of the base plate 145 and ruler mounting plate 153 will be locked by being held between the presser 159 and the flange of the Threaded rod 157.

The operation of moving the head 102 and ruler members 164 and 165 upwardly away from the surface of the drawing board 11 and bringing the same into an upright position to as follows: If the handle 130 is pulled upwardly by hand, the head 102 and ruler members 164 and 165 will move upwardly in a predetermined range into a position in which they are maintained parallel to the surface of the drawing board 11, because the member 108 and Y-carsol 74 are connected to each other by the pantagraph head connecting mechanism 103. Moreover, if the handle 130 is pulled upwardly in a direction in which the ruler members 164 and 165 are brought into an upright position with respect to the surface of the drawing board 11, the pantagraph head connecting mechanism 103 immediately loses its parallelgrammic shape, with the relief slot 118 formed in the connecting ring 117 moving in sliding motion along the screw 121 and the lower side of the parallelogram being elongated, thereby bringing the head 102 and ruler members 164 and 165 into a position in which they are upright with respect to the surface of the drawing board 11.

1f the knob 128 is turned to rotate the threaded rod 124 while the head 102 and ruler members 164 and 165 are disposed parallel to the drawing board 11 with the undersides of the former being maintained in intimate contact with the surface of the latter, the slide block 123 threadably connected to the threaded rod 124 will move downwardly along the guide opening 122 and the resilient force of the spring 129 acting on the slide block 123 will increase in intensity in proportion to the increase in the distance of downward movement of the slide block 123. As a result, the connecting member 111 will be pivotally moved upwardly about the screws 112 and 113 by the resilient force of the spring 129, so that the head 102 and ruler members 164 and connected to the connecting member 111 will move upwardly a predetermined distance from the surface of the drawing board 11 while being maintained parallel thereto.

The intensity of the resilient force required for moving the head 102 and ruler members 164 and 165 upwardly away from the surface of the drawing board 11 may vary depending on the angle of inclination of the drawing board 11. It is possible to move the head 102 and ruler members 164 and 165 upwardly away from the surface of the drawing board 11 with a resilient force of lower intensity when the angle of inclination is greater than when the angle of inclination is smaller. Accordingly, when the angle of inclination of the drawing board 11 is varied with respect to the horizontal, it is required to adjust the resilient force of the spring acting on the connecting member 111 by turning the knob 128 an amount which may vary depending on the variation in the angle of inclination.

When it is desired to reduce frictional dragging of the head 102 and ruler members 164 and 165 on the drawing board 11, it will not be necessary to move them upwardly by the biasing force of the spring 129 so that their undersides will be completely spaced apart from the surface of the drawing board. To this end, the resilient force of the spring 129 acting on the connecting member 111 may be adjusted such that the biasing force is sufficiently high in intensity to reduce the frictional dragging while the head 102 and ruler members 164 and 165 are maintained in contact with the drawing board 11.

While this invention has been shown and described as using a plate spring as resilient means for moving the head and ruler means upwardly away from the drawing board, it is to be understood that resilient means of any other suitable form may be used so long as it exerts a resilient force on the ruler means and head.

In the embodiment shown, the spring 129 or resilient means is resiliently maintained in contact with the connecting member 111. It is to be understood, however, that this invention is not limited to this specific construction, and that the resilient means 129 may be arranged such that its resilient force acts directly on the head 102. Alternatively, the ruler members 164 and 165 may be connected to the head 102 such that they can be moved away from or into contact with the surface of the drawing board 11 so as to cause the biasing force of the resilient means only to act on the ruler members 164 and 165 and not on the head 102. Since the underside of the head 102 is maintained in point contact with the surface of the drawing board 11 through the convex curve portions 151, the frictional dragging of the head 102 on the drawing board is not so great as the frictional dragging of the ruler members 164 and 165 on the drawing board 11.

We claim:

1. A drawing instrument comprising a drawing board, an X-rail fixed to one marginal portion of said drawing board, a Y-rail slidably connected to said X-rail at right angles thereto and movable parallel to the surface of said drawing board, a Y-carsol slidably mounted on said Y-rail, a head, ruler means with graduated scales, mounting means mounting said ruler means on said head for angularly moving said ruler means to any degree as desired, a pantagraph mechanism mounting said head on said Y-carsol for moving the head and ruler means away from and into contact with the surface of the drawing board while said head is maintained parallel to the surface of the drawing board, and resilient means between said Y-carsol and said pantagraph mechanism for resiliently moving said pantagraph mechanism upwardly so as to thereby resiliently move said head and said ruler means upwardly away from the surface of the drawing board. v

2. A drawing instrument as claimed in claim 1 wherein said pantagraph mechanism has at least one supporting link on the lower side of said pantograph mechanism movable relative to the remainder of said pantograph mechanism so that said lower side is extensible relative to the upper side of the pantograph mechanism.

3. A drawing instrument as claimed in claim 1 wherein said pantograph mechanism comprises a connector constituting one side thereof and having a reciprocably slidable block therein exposed at the bottom thereof, and said resilient means is secured to the Y- carsol and has a free end thereof in engagement with the exposed end surface of said slide block, and means on said connector engaged with said slide block to reciprocate said slide block, whereby the resilient force of said resilient means acting on said connector can be varied by moving said slide block. 

1. A drawing instrument comprising a drawing board, an X-rail fixed to one marginal portion of said drawing board, a Y-rail slidably connected to said X-rail at right angles thereto and movable parallel to the surface of said drawing board, a Y-carsol slidably mounted on said Y-rail, a head, ruler means with graduated scales, mounting means mounting said ruler means on said head for angularly moving said ruler means to any degree as desired, a pantagraph mechanism mounting said head on said Ycarsol for moving the head and ruler means away from and into contact with the surface of the drawing board while said head is maintained parallel to the surface of the drawing board, and resilient means between said Y-carsol and said pantagraph mechanism for resiliently moving said pantagraph mechanism upwardly so as to thereby resiliently move said head and said ruler means upwardly away from the surface of the drawing board.
 2. A drawing instrument as claimed in claim 1 wherein said pantagraph mechanism has at least one supporting link on the lower side of said pantograph mechanism movable relative to the remainder of said pantograph mechanism so that said lower side is extensible relative to the upper side of the pantograph mechanism.
 3. A drawing instrument as claimed in claim 1 wherein said pantograph mechanism comprises a connector constituting one side thereof and having a reciprocably slidable block therein exposed at the bottom thereof, and said resilient means is secured to the Y-carsol and has a free end thereof in engagement with the exposed end surface of said slide block, and means on said connector engaged with said slide block to reciprocate said slide block, whereby the resilient force of said resilient means acting on said connector can be varied by moving said slide block. 